A conventional digital copying machines is disclosed, for example, in Japanese Patent Application Laid-Open No. 9-186836. This digital copying machine picks-up an image of a manuscript, converts the picked up image into image data, and stores the image data of one page or a plurality of pages in an auxiliary storage device such as a floppy disk device or a hard disk device. The image data in the auxiliary storage device is then transferred to a frame memory. The image data in the frame memory is then sent to a printer engine page by page. Accordingly, the image of the manuscript is reproduced.
A control system of this digital copying machine has a configuration as shown in FIG. 14. This control system includes two CPUs, i.e., CPU 1 and CPU 2 for controlling the whole digital copying machine, a main storage memory 3 for storing application programs to be executed by these CPUs and font data required when printing the image of the manuscript, and a CPU bus 30 for connecting the CPU 1, CPU 2, and the main storage memory 3 to each other. The application programs and font data are read out from an auxiliary storage device 21 and stored in the main storage memory 3.
The CPU bus 30 is connected to a PCI bus 31 via a PCI bridge 4, and connected to a PCI bus 32 via a PCI bridge 5. The CPU bus 30 is also connected to a PCI bus controller 6 to which the PCI bridge 4 and the PCI bridge 5 are connected.
The PCI bus controller 6 conducts arbitration between the PCI bus 31 supported by the PCI bridge 4 and the PCI bus 32 supported by the PCI bridge 5 and effecting control corresponding to a PCI bus protocol.
There are connected to the PCI bus 31, a display controller 7 for controlling operation of a display device 10, a touch panel controller 8 for controlling operation of a touch panel 9, an FD/HD interface controller 11 for controlling operation of the auxiliary storage device 21 such as a floppy disk device or a hard disk device, a serial parallel interface controller 12 for conducting serial communication and parallel communication with a host computer which is not illustrated, and a network interface controller 13 for conducting communication with a local area network or the like.
A DRAM controller 14 is also connected to the PCI bus 31. The DRAM controller 14 generates an address for writing and reading image data into/from a frame memory 16, and effects refresh control of a DRAM included in the frame memory 16.
On the other hand, there are connected to the PCI bus 32 a DRAM controller 15, a DMA controller 18, and a SCSI interface 20. The DRAM controller 15 generates an address for writing and reading image data into/from a frame memory 17, and effects refresh control of a DRAM included in the frame memory 17. The DMA controller 18 effects transfer control of image data of DRAMs included in the frame memory 16 and the frame memory 17. The SCSI interface 20 effects connection control to a SCSI bus which is not illustrated.
The DRAM controller 14 is connected to the DMA controller 18 and a video interface 19. The DRAM controller 15 is also connected to the DMA controller 18 and the video interface 19. The DMA controller 18 can transfer image data developed in the frame memory 16 directly to the video interface 19 by using DRAM transfer control, and transfer image data developed in the frame memory 17 directly to the video interface 19 by using DRAM transfer control. Image data transferred to the video interface 19 is transmitted to a printer engine which is not illustrated.
Operation of the conventional digital copying machine having the configuration heretofore described will now be described by referring to the case where the copying machine reads an image of a manuscript extending over a plurality of pages and prints the image of the manuscript. Image data including character codes and control commands inputted from a host computer which is not illustrated via the serial parallel interface controller 12 or inputted from a local area network or the like which is not illustrated via the network interface controller 13 is inputted to the CPU 1 (or CPU 2) via the PCI bus 31, the PCI bridge 4, and the CPU bus 30, decoded by the CPU 1, and developed on, for example, the frame memory 17 as bit map data.
When bit map data of the image corresponding to one page of a manuscript is developed on the frame memory 17, the CPU 1 starts the DMA controller 18, and transfers the bit map data of the image corresponding to one page of the manuscript from the frame memory 17 to the video interface 19. On the basis of the transferred bit map data, a printer engine (not illustrated) prints the image of the read manuscript.
Recently, however, there is a movement on foot to suppress discharge of carbon dioxide to the utmost in order to prevent the warming of the earth. As a part of this movement, various energy saving measures are being taken in various business machines, such as home electric products, personal computers, and OA machines, as well. The degree of demand of energy saving is increasing day by day.
In order to accede to such a demand, a recent digital copying machine recognizes that it has not been used for a long time, automatically comes in a power saving mode, and cuts off power supply of a heater section of a fuser consuming comparatively great power among components of the digital copying machine.
If the degree of the demand of energy saving further increases, however, it is inevitable that even a control device which consumes comparatively small power among the components of the digital copying machine is pressed for the energy saving measure. The control device is not a terminal device unlike the heater section of the fuser, but it is a principal device for controlling the operation of the digital copying machine. Unlike the heater section of the fuser, therefore, the energy saving measure of the control device cannot be finished by merely cutting off the power supply.
For example, in the case of the digital copying machine shown in FIG. 14, function blocks such as various controllers are connected to each other by buses such as the CPU bus 30, the PCI bus 31 and the PCI bus 32. Therefore, it is difficult to cut off the power supply of some function blocks as the energy saving measure, because there is a fear that the function of the digital copying machine itself may stop. For example, in the PCI bus, existence of a PCI card is sensed by inserting the PCI card into a slot. Therefore, it is not possible to cut off the power supply of only some PCI cards on a PCI bus.
As a simple energy saving measure, therefore, it is conceivable to cut off the power supply of all controllers. However, there are function blocks taking charge of functions which must not be stopped such as a FAX function (especially its reception function). Therefore, such an easygoing energy saving measure cannot be adopted.